A member in my ward gets regular welfare assistance with her rent. Her landlord has moved locations a few times in the last couple of months so those checks have been lost. What is the procedure for voiding checks and reissuing if you have no way of getting those checks in your possession?

See Voiding a Check on the Record-Keeping and Technology Support site. Basically, if you don't have the check in your possession, you need to call Local Unit Support to stop payment on the check. Once that's done, they'll tell you to go ahead and void the check in MLS as usual.